- Fiber Optic Cable Installation
Portland General Electric (PGE) plans to install a fiber optic cable on the Grizzly-Round Butte 500-kV circuit. The installation will provide reliable high-speed data between PGE and Bonneville Power Administration (BPA) resources. We were contracted to develop a construction package for installation of fiber optic cable on the existing transmission line.
The Grizzly to Round Butte 500-kV transmission line is 16 miles long in central Oregon. The line features lattice steel towers and traverses generally flat terrain with road and farmland crossings. 7#8 Alumoweld cable was the existing shieldwire, and the proposed optical ground wire (OPGW) was AFL DNO-8234 AC-58/513.
We performed an initial study to compare the loads between the existing and proposed cables. The new OPGW had a slightly larger diameter, and higher loads would be present under ice and/or wind conditions than on the existing cable. This prompted modeling of the existing lattice towers for structural analysis. The analysis exposed six towers with some overstressed members under a few loading conditions. Reinforcement of those members were designed and incorporated into the construction package.
Our team also performed an electrical study on the line, examining the short duration current capacity of the OPGW, power losses of a fully grounded OPGW, and safety concerns with a fully grounded vs. sectionalized OPGW. The client used the study determine the expected operation of the system and effects of sectionalizing the OPGW.
Our focus was to provide a reliable communication path design with consideration for structure integrity, safety, constructability and maintainability.
- Detailed engineering
- Material procurement support
- Permitting support
- Construction support
- Electrical study support
- Install OPGW fiber cable on existing lattice steel towers
- File with FAA and design to meet recommendations
- Lattice tower structural analysis and reinforcement designs
- Electrical study performed to determine pros and cons of sectionalizing OPGW